The present invention relates to an apparatus and a method for production control whereby checks are made to determine if a workpiece to be loaded into a given working device is suitable for undergoing the work to be done by that particular device.
Recent years have seen an unremitting increase in the number of steps to fabricate semiconductor devices such as static random access memories (SRAMs), dynamic random access memories (DRAMs), and charge-coupled devices (CCDs) to accommodate their ever-increasing degrees of circuit integration. In the area of production control over such complicated semiconductor fabrication facilities, one crucial issue is the prevention of what is known as cross contamination across different processes or devices of production.
For example, if a wafer with a metal wiring substance such as aluminum formed thereon is inadvertently loaded into a gate oxidation furnace for thermal oxidation, the furnace will be contaminated by the metal. When the contaminated device is used to work on another lot of workpieces, the entire lot will be contaminated. The contaminated lot of workpieces will move on to other devices which are in turn polluted by the contaminated workpieces. Such a chain-reacting process of cross contamination, once taking place, accelerates over time and causes extensive damage throughout the production line.
In related art production control setups, engineers in charge of production processes and devices are supposed to check for any signs of cross contamination in each step of fabrication. As the number of fabricating steps increases, however, these checks tend to be performed insufficiently; some checks may be made incorrectly and some may even be neglected altogether.